1. Field of the Invention
The present invention relates to a method for manufacturing a wire harness that includes a flexible circuit belt, such as a flexible flat cable (FFC) or a flexible printed circuit (FPC), and one or more branch connection terminals attached to the flexible circuit belt.
2. Description of the Related Art
In general, a terminal connector is used to electrically connect a flat circuit, such as a flexible flat cable or a flexible print board, to another circuit. Such a terminal connector is generally attached to an end portion of the flat circuit, and a counterpart connector of another circuit to be connected receives the terminal connector of the flat circuit.
FIG. 1 illustrates an example of the conventional terminal connection structure of a wire harness, which is disclosed in, for example, Japanese Utility Model Registration No. 2549583. To fabricate the conventional terminal connection structure, multiple slips 2A are formed in advance at an end portion of the flexible print board 2 before multiple connection terminals 1 are attached to the flexible print board 2. The slits 2A make the flexible print board 2 branch off. Each connection terminal 1 is fixed to one of the branches of the flexible print board 2 by making the claws of each connection terminal 1 pierce through a conductive pattern 3 of the flexible print board 2.
The connection terminals 1 and the branches of the flexible print board 2 are then inserted in the cavities 4A of a connector housing 4, as shown in FIG. 1B.
However, it is difficult and troublesome for the conventional technique for fabricating the terminal connection structure of a wire harness to accurately position the connection terminals 1 with respect to the flexible print board 2. This is because the slits 2A are formed in advance at the end portion of the flexible print board 2, and the branches can not stay at the proper position in a stable manner. If any one of the connection terminals 1 is offset relatively from the corresponding branch of the flexible print board 2, the claws of that connection terminal 1 do not correctly pierce through the conductive pattern 3 of the flexible print board 2. In this case, electric connection between the flexible print board 2 and the connection terminal 1 is lost.
In addition, the branches of the flexible print board 2, which are defined by the slits 2A prior to fixing the connection terminals 1, are likely to deform under an external force or a stress during a manufacturing process of a wire harness. Such an external force or a stress is easily applied to the branches by pulling or drawing the flexible print board 2 around. This means that the conventional method for fabricating a wire harness requires careful and cautious handling of the flexible print board 2 so as not to apply any excessive stress or a tension to the branched portions of the print board 2.
Therefore, it is an object of the invention to overcome these problems in the prior art technique, and to provide a method for fabricating a wire harness with branch connection terminals, which can guarantee both mechanical and electric connection between each terminal and the wire harness. This method can also efficiently prevent displacement or offset of the connection terminals from the proper position on a flexible circuit belt used in the wire harness.
To achieve the object of the invention, a method for fabricating a wire harness first takes the step of preparing a flexible circuit belt by arranging multiple conductive strips in parallel to each other at a predetermined interval, and sandwiching the conductive strips with a pair of base films. Then, multiple connection terminals, each having a contact and a plurality of projections, are fixed to the end portion of the flexible circuit belt by causing the projections of each connection terminal to pierce through one of the conductive strips. The number of connection terminals is equal to the number of the conductive strips. Finally, one or more slits are formed between any two adjacent conductive strip so as to extend from the end of the flexible circuit at a predetermined length.
The flexible circuit belt is cut into branches by forming the slits. Consequently, multiple branch terminals are formed, each consisting of a branch portion of the flexible circuit belt and a connection terminal fixed to that branch portion.
With this method, the end portion of the flexible circuit belt is branched out after the connection terminals are fixed to the flexible circuit belt. Because the end portions of the conductive strips are fixed when the connection terminals are attached to the connection area of the flexible circuit belt, the connection terminals are reliably attached to the designed positions without being offset from the conductive strips.
With an alternatively method, a flexible circuit belt is first prepared by arranging multiple conductive strips in parallel to each other at a predetermined interval, and sandwiching the conductive strips with a pair of base films. Then, a row of slots is formed between any two adjacent conductive strips at a predetermined distance from the end of the flexible circuit belt. A connection area is defined between the end of the flexible circuit belt and the row of slots. Then, multiple connection terminals, each having a contact and a plurality of projections, are fixed to the connection area of the flexible circuit belt by causing the projections of each connection terminal to pierce through one of the conductive strips. Finally, one or more slits are formed from the end of the flexible circuit belt so that the slits extend between any two adjacent conductive strips and communicate with the associated slots.
In this case, the slots are formed in the flexible circuit belt before the connection terminals are fixed to the end portion of the flexible circuit belt. The slots formed at a predetermined distance from the end of the flexible circuit belt allow the flexible circuit belt to be cut into branches easily after the projections of each connection terminal pierce through the conductive strips. The branch terminals formed in this manner are smoothly inserted in the connector housing.
In another aspect of the invention, a wire harness comprising a flexible circuit belt folded in double is fabricated. With this method, a flexible circuit belt is prepared first by arranging multiple conductive strips in parallel to each other at a predetermined interval and sandwiching the conductive strips with a pair of base films. Any two adjacent conductive strips define a non-conductive region between them. Then, two rows of slots are formed in the middle of the flexible circuit belt in such a manner that two slots are aligned along the longitudinal axis of each non-conductive region of the flexible circuit belt at a predetermined distance between them. The two rows of slots are symmetrical with respect to a centerline extending in the width direction of the flexible circuit belt between the rows. Then, the flexible circuit belt is folded in double along the centerline between the two rows of slots so that a row of slots lies on top of the other row of slots. Then, multiple connection terminals, each having a contact and a plurality of projections, are fixed to the folded portion of the flexible circuit belt by causing the projections of each connection terminal to pierce through one of the doubled conductive strips of the folded flexible circuit belt. Finally, one or more slits are formed between any two adjacent conductive strips from the folded edge of the flexible circuit belt so as to communicated with the overlaid slots.
With this method, again, the folded flexible circuit belt is branched out after the connection terminals are fixed to it. Accordingly, positioning of the connection terminals with respect to the associated conductive strips is carried out accurately, and electrical connection between the flexible circuit belt and the connection terminal is guaranteed.
In either method, the flexible circuit belt may be prepared by forming conductive strips on a first base film, and forming a second base film over the conductive strips and the first base film. The base film is preferably an insulating film.